Sputter deposition of thin film MIM capacitors on LTCC substrates for RF bypass and filtering applications

Abstract

Thin film capacitors for RF bypass and filtering applications were sputter deposited onto low temperature co-fired ceramic (LTCC) substrates. The capacitors were configured in a metal-insulator-metal (MIM) design featuring 200 nm thick Al electrodes and a 300 nm thick Al2O3 dielectric layer, with dimensions varied between ∼150×150 μm and ∼750×750 μm. DC current-voltage measurements (E ≤ 5 MV/cm) coupled with impedance analysis (≤15 MHz) was used to characterize the resulting devices. More than 90% of the devices functioned as capacitors with high DC resistance (>20 MΩ) and low loss (tan δ <0.1). A second set of capacitors were made under the same experimental conditions with device geometries optimized for high frequency (≥200 MHz) applications. These capacitors featured temperature coefficient of capacitance (TCC) values between 500 and 1000 ppm/°C as well as low loss and high self-resonant frequency performance (ESR <0.6 Ohms at self-resonance of 5.7 GHz for 82 pF). Capacitance and loss values were comparable between the capacitor structures of similar areas at the different frequency regimes.